The present invention relates to reel-type slot machines, and more particularly to reel-type slot machines having multiple display reels each bearing a plurality of different game symbols, wherein the reels are driven to display game symbols selected for each reel by a random number generator and look-up table. An undesired game result may be avoided by reducing or omitting it from the look-up table.
In recent years reel-type slot machines have evolved from mechanical type machines wherein mechanical clutches were relied on to stop spinning display reels at random locations to display a game result, to electronic type machines wherein a microprocessor randomly selects a game result, and the display reels are driven to reel positions wherein game symbols on the reels display the game result. The present invention is directed to an improvement in such an electronic type slot machine wherein a random number generator randomly selects a number within a predetermined set of random numbers, the randomly selected number is associated with a game symbol for each reel within a look-up table, and each reel is positioned to display its respective game symbol. By providing a greater number of random numbers in the random number set than the number of available sets of different symbol combinations which can be displayed on the reels, and by varying the sizes of the subsets of random numbers which correspond to each different set of game symbols, the probability of a particular game result occurring can be predetermined for the machine. An undesirable game result can be avoided by reducing its subset to zero.
In electronic reel type slot machines the reels are typically positioned by stepper motors, which may be contained in removable modules within the machine. The stepper motors respond to applied signals which are progressively phase-shifted relative to each other such that the stepper motors are caused to turn one element of rotation for each progression of the phase signals.
The phase signals are typically generated in motor drive circuits, which respond to applied motor stepping pulses to advance the reels in increments. The motor stepping pulses are generated by a microprocessor, a predetermined number of pulses being applied to the motor drive circuits to cause each motor to be incremented to a selected stopping position wherein the game result is displayed by the display reels. In prior slot machine designs, the stopping positions were typically determined by the microprocessor by either counting the number of motor pulses occurring after a "home" marker on the reel had passed a fixed sensor, or by counting markers provided on the reel for each symbol position after the home marker had passed.
In contrast, the present invention is directed to a reel-type slot machine wherein in response to a play command the microprocessor selects a random number within a predetermined set of random numbers, the selected random number is associated with game symbols within a memory device providing a look-up table, and the display reels are rotated to display the game symbols.
Accordingly, it is a general object of the present invention to provide a new and improved reel-type slot machine.
It is a more specific object of the present invention to provide a reel-type slot machine wherein game symbols to be displayed are selected by a random number generator operating in conjunction with a look-up table, and the display reels are driven by stepper motors to display the selected game symbols.